The present invention relates to thermoformed abrasive articles and processes therefor. Still more particularly the present invention relates to an abrasive pad or other abrasive articles such as a lapping tool, abrasive wheels and the like which are injection molded.
In the past, the use of abrasive pads, which include abrasive resinoid segments attached to backing substrates, has been common when polishing stones and marbles and other materials. Because of the relatively thick and non-yielding resinoid segments generally used in these pads, it has been problematic to provide a flexible type abrasive pad using these types of segments. In the past, these segments have been attached to backing substrates, such as fabrics or the like, utilizing a large number of small segments to produce a flexible abrasive pad. Such abrasive pads are commonly used on rotary polishers for finishing of marble floor surfaces, for instance. While these structures have been useful as rotary polishing pads, the operational life of the pads has been low. This is because of disattachment of segments during use.
Therefore, it has been a goal in the art to produce a long lasting flexible "segmented-type" abrasive sheet material which will have increased durability and be less subject to loss of abrasive portions during use. This goal has lead to the discovery that thermoplastics can be used in abrasive pads as is set forth in my prior patent application, U.S. Ser. No. 526,055, filed May 21, 1990, for "Flexible One-Piece Diamond Sheet Material With Spaced Apart Abrasive Portions" and U.S. Ser. No. 732,503, filed Jul. 18, 1991, entitled "Injection Molded Abrasive Pad".
It has now been discovered that a broad range of abrasive articles can be injection molded in an economical and efficient process. In the past, thermosets or thermoset-like materials have primarily been utilized for abrasive articles because of their ability to withstand the high temperatures associated with abrasive operations. For purposes herein thermoset refers to polymer materials which chemically cross-link and are not re-workable at substantially the same temperature.
However, the manufacture of abrasive articles with thermoset or thermoset-like materials is costly because of the relatively slow batch type manufacturing processes and the costs of materials involved. The use of an injection molding process with thermosets or thermoplastics has been thought to be impractical because of the anticipated wear on the injection molding apparatus. Additionally, some of the extremely high melting point thermoset-like compositions are costly and impractical for production of abrasive articles.
Therefore, it is a goal in the present invention to provide an abrasive pad which can be efficiently manufactured.